Touch screens that utilize capacitive sense arrays are widely applied in today's industrial and consumer product markets. Capacitive sense arrays can be found in cellular phones, GPS devices, set-top boxes, cameras, computer screens, MP3 players, digital tablets, and the like, replacing mechanical buttons, knobs, and other conventional user interface controls. A capacitive sense array is often disposed below a touch sensing surface of a touch screen, and includes an array of capacitive sense elements. Capacitances of these capacitive sense elements vary when an object (e.g., a finger, a hand, a stylus, or another object) comes into contact with or hovers above the touch sensing surface. A processing device coupled to the capacitive sense array then measures the capacitances of the capacitive sense elements and/or identifies capacitance variations of the capacitive sense elements for determining a touch or presence of the object associated with the touch sensing surface. The use of the capacitive sense array has offered a convenient and reliable user interface solution that is feasible under many harsh conditions, so capacitive sense arrays made of capacitive sense elements have been widely used in many industrial and consumer products.
Under some circumstances, touch locations cannot be determined from the capacitive sense arrays effectively and efficiently when one or more unwanted factors are involved in touch detection. For example, water present on the touch sensing surface can interfere with touch signals associated with normal touches. Finger temperature may also compromise touch signals associated with a touch of a finger. In some situations, false touches need to be suppressed when a user holds a touch sensing surface with a grip on or near an edge of the touch sensing surface or when touch signals are corrupted by noise. New touch sensing devices that overcome the detrimental impact from some or all of these unwanted factors are desirable.